The Holt Research Forest is a 120-hectare (300 acre) forest located in Arrowsic, Maine. Arrowsic is similar to the peninsulas of the mid-coast region, but is actually an island surrounded by the Kennebec River to the west and south, the Sasanoa River to the north and east, and the Back River to the east. The island falls within Maine’s coastal climatic region and the midcoast biophysical region of Maine. This region has the greatest woody plant species richness in the state in part because it falls within the transition between the Northeastern coastal forest to the west and south and the New England/Acadian forest to the east and north. The soils are derived from shallow glacial deposits on ridges and deep glaciomarine sediments in low-lying areas.

The forest is predominantly a dry ridge, oak-pine ecosystem typical of mid-coastal Maine. Parts of the property were farmed from the late 1600s to the 1940s, but most of the cleared land was abandoned by the early 1900s, resulting in a canopy that in 1983 was dominated by 60- to 80-year-old trees. Today the most abundant tree species by volume and number are Eastern White Pine (Pinus strobus), Northern Red Oak (Quercus rubra), and Red Maple (Acer rubrum). The oldest trees were 125-year-old, heavy-limbed, eastern white pines and eastern hemlocks that grew along fence rows and drainage ways, a few still remain today. The understory includes shrubs such as blueberry (Vaccinium sp.), huckleberry (Gaylussacia baccata), and juniper (Juniperus communis). Common herbs include Canada mayflower (Maianthemum canadense), bunchberry (Cornus canadensis), wintergreen (Gaultheria procumbens), partridge berry (Mitchella repens) and starflower (Trientalis borealis). For a complete plant species list go here.